Flash Furnace Off-Gas Cooling in a Plate Column: Reduction of Pressure Drop by Column Design Modification

In the early 1990s, the Inco SO2 abatement project which aimed at a 60% reduction in SO2 emissions from the Copper Cliff Smelter included the installation of two new flash furnaces (the first in 1991 and the second in 1993). The flash furnace off-gas is cooled and cleaned through two new Monsanto Dynawave gas cleaning systems that replaced the traditional venturi scrubbing system. It was discovered that the flash furnace production capacity is often limited by the capacity of the gas cleaning system. The key task is to reduce the pressure drop in the system. The froth column which cools the gas from about 85 to 25 °C is responsible for the largest pressure drop in the gas cleaning system. Initially, the column was fitted with 22 plates, but in 1994, both #1 and #2 froth columns were modified by reducing the number of plates in each column from 22 to 18 and increasing the interplate spacing on the lower plates. With recent increasing demand for more throughput in the flash furnaces, excessive pressure drops have again become a limiting factor. In 2005, further modifications of the froth columns were made on the basis of recent data and estimates of the actual volume flows of gas within the column. The bottom plate (#18) of each column was removed and two small deflector baffles were added to reduce liquor entrainment at the bottom of the column. These modifications have reduced the overall gas pressure drops by just under 20% leading to a much improved operation of the gas cleaning system.